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Case Closure Summary Page 2 <br /> Leaking Underground f=uel Storage Tank.Program <br /> 111 Release and Site Characterization Information (continued) <br /> I� <br /> y <br /> Maximum Documented Contaminant Concentrations - - Before and After Cleanup <br /> Contaminant Soil Before Soil Water Water Contaminant Soil Soil Water Water <br /> After Before After Before After Before After <br /> TPH (Gas) 11,000 ---- 12 0.21 MTBE 3.6 ---- 0.053 <0.0005 <br /> Benzene 0.24 ---- 0.82 0.004 Lead 330 ---- ---- ---- <br /> Toluene 350 ---- 0.073 <0.0005 EDB ---- ---- ND <0.0005 <br /> Ethylbenzene 160 ---- 1.3 0.0043 1,2-OCA ---- ---- 0.077 <0.0005 <br /> Xylene 750 ---- 0.91 0.018 Oxygenates ---- ND <0.0005 <br /> All results listed above are in parts per million (ppm) <br /> "Soil After"column was left unfilled because no remediation cleanup was ever implemented at the site. One soil sample at <br /> 1.5 feet bsg collected at the dispenser in 1987 during the tank removal had a concentration of 330 ppm of lead, the STLC <br /> for the sample was 6.9 ppm of lead. Soil samples from 15 feet and from the stockpile were significantly less at between <5 <br /> and 14 ppm STLC. <br /> "Water Before" results were from a combination of grab water samples from initial investigation in 1998, and samples from <br /> monitoring well#3 (the only consistently contaminated monitoring well) in 1999 and early 2000. Concentrations of the <br /> contamination in the monitoring wells have fallen significantly since then. "Water After"column reflects the latest quarterly <br /> monitoring results in 2002. <br /> MTBE was previously detected using Method 8020, but subsequent analysis by Method 8260 were either non-ddtect or in <br /> very low concentration (<5.0 ggll). Investigation showed minimal impact to soil and groundwater. Beneficial uses of <br /> groundwater are protected, now and in the future. <br /> IV. Closure <br /> Does completed corrective action protect existing beneficial uses per the Regional Board Basin Plan? Yes <br /> Does completed corrective action protect potential beneficial uses per the Regional Board Basin Plan? Yes <br /> Does corrective action protect public health for current land use? Yes <br /> Site management requirements: none <br /> Should corrective action be reviewed if land use changes? Yes <br /> Monitoring wells decommissioned: NIA Number Decommissioned: 0 Number retained: 5 <br /> List enforcement actions taken: NOR sent <br /> List enforcement actions rescinded: None <br /> V. Local Agency Representative Data <br /> Name: Margaret Lagorio Title: Supervising REHSISite Mitigation/LOP Unit IV. <br /> Signature: Date: <br /> Vl. Central Valley Regional Water Quality Control Board R13Notification <br /> Date Submitted to RB: Response Date: <br /> RB Staff: Marty Hartzell Response: <br /> Title: Assoc Eng Geologist <br /> VII. Additional Comments, Data, etc. <br /> Remaining wells on site must be destroyed before final closure can be granted. <br /> This document and the related CASE CLOSURE LETTER,Shall be retained by the lead agency as part of the <br /> official site file. (08124193) Exhibit N Page 2 of 2 <br />